Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Emission Control Function Monitoring & Comprehensive Component Monitoring
OBD II regulations are based on section 1968.1 of Title 13, California Code of Regulations (CCR), The law set forth in section 1968.1 requires an increased scope of monitoring emission related control functions including:
- Catalyst Monitoring
- Heated Catalyst Monitoring (currently used on BMW 750iL vehicles)
- Misfire Monitoring
- Evaporative System Monitoring
- Secondary Air System Monitoring
- Air Conditioning System Refrigerant Monitoring (Not applicable for BMW vehicles)
- Fuel System Monitoring
- Oxygen Sensor Monitoring
- Exhaust Gas Recirculation (EGR) System Monitoring (Not applicable for BMW vehicles)
- Positive Crankcase Ventilation (PCV) System Monitoring (Not required at this time).
- Thermostat Monitoring (if equipped)
Monitoring these emission requirements is a function of the ECM which uses "data sets" while monitoring the conditions of the environment and the operation of the engine using existing input sensors and output actuators.
The data sets are programmed reference values the ECM refers to when a specific monitoring procedure is occurring. If the ECM cannot determine the environmental and/or engine operating conditions due to an impaired or missing signal, it will set a fault and illuminate the "Malfunction Indicator Light".
This input or control signal monitoring falls under another category called "Comprehensive Component Monitoring" . The ECM must recognize the loss or impairment of the signal or component. The ECM determines a faulted signal or sensor via three conditions:
- Signal or component shorted to ground.
- Signal or component shorted to B+.
- Signal or component lost (open circuit).
Specific fault codes are used to alert the diagnostician of these conditions.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.